1. Field of the Invention
The present invention relates to subsea production of hydrocarbons. More specifically, the invention relates to a system and method to provide flow/pressure boosting in a subsea environment.
2. Description of the Related Art
Petroleum development and production must be sufficiently profitable over the long term to withstand a variety of economic uncertainties. Booster pumping is increasingly being used to aid in the production of wellhead fluids. Subsea installations of these pumps are particularly helpful in producing remote fields and many companies are considering their use for producing remote pockets of oil and for producing deep water reservoirs from remote facilities located in shallower water. Such booster pumps allow producers to transport multiphase fluids (oil, water, and gas) from the wellheads to remote processing facilities (instead of building new processing facilities near the wellheads and often in deep water). These booster pumps also allow fluid recovery at lower final reservoir pressures before abandoning production. Consequently, there is a greater total recovery from the reservoir.
For deep water reservoirs, booster pumps are used to transport wellhead fluids from deep water wellheads to remote processing facilities located in shallower water. While there are a number of technical difficulties in this type of production, the cost savings are very large. Consequently, producers would like to transport wellhead fluids from the seafloor in deep waters through pipelines to remote processing facilities in moderate water depths. Transport distances of tens of kilometers are not uncommon with longer distances currently in the planning stages.
Commonly available booster pumping systems commonly include a submersible pump installed in the producing well or a pumping system connected to a subsea Christmas tree manifold attached to the wellheads from which fluids flow as a result of indigenous reservoir energy. The other end of the pumps are connected to a pipeline which transports the fluids from the wellhead to the remote processing site. Submersible pumps and their operation, including their installation, are well known and understood in the art. A problem, however, is that should a failure occur, valuable production flow can be interrupted while the pump is repaired. Subsea pumping systems connected externally to the producing well are typically unique to each application and require modifications and adaptations of surface pumps to the subsea environment. Such systems are typically more expensive and more difficult to install than submersible pumps.
Wellhead fluids can exhibit a wide range of chemical and physical properties. These wellhead fluid properties can differ from zone to zone within a given field and can change with time over the course of the life of a well. Furthermore, well bore flow exhibits a well-known array of flow regimes, including slug flow, bubble flow, stratified flow, and annular mist, depending on flow velocity, geometry, and the aforementioned fluid properties. Consequently, the ideal pumping system should allow for a broad range of input and output parameters without unduly compromising pumping efficiency and service life. Submersible pumps typically operate at conditions of lower gas fractions than seafloor mounted systems and thus exhibit fewer problems from such multi-phase flows.
The methods and apparatus of the present invention overcome the foregoing disadvantages of the prior art by providing a submersible pump system that provides flow/pressure boosting and does not jeapordize production flow during downtime.
The present invention contemplates a subsea pumping system for boosting the flow energy of a production flow.
In one aspect, the present invention is a system for producing hydrocarbon fluids from a subsea formation, comprising at least one producing well penetrating the formation for producing hydrocarbon fluids. At least one dummy well is hydraulically connected to the at least one producing well for routing the hydrocarbon fluids from the producing well to the dummy well. At least one pump is disposed in the at least one dummy well. The pump takes suction flow from the dummy well and boosts the flow energy of the discharge flow of hydrocarbon fluids.
In another aspect, the present invention describes a method for producing hydrocarbon fluids from a subsea formation, comprising installing at least one pump in at least one dummy well where the dummy well is hydraulically connected to at least one producing well. The at least one dummy well acts as a suction reservoir for the pump. Production flow is routed from the producing well to the dummy well where the pump is used for imparting flow energy to the production flow.
Examples of the more important features of the invention thus have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto.